The present invention relates, in general, to devices for reducing aerodynamic drag on road vehicles, and, more particularly, to an air deflector for directing air flow around and under the rear suspension, axles, wheels, tires, brake chambers, slack adjusters, and hangers under vehicles such as trucks and trailers.
Trucks, and particularly tractor-trailer units having multiple rear wheels, present a high resistance to air flow with the rear wheels, suspension, and other mechanical components at the rear of the vehicle interfering with the smooth flow of air around and under the vehicle. This interference creates turbulence and a high aerodynamic drag which results in high fuel use and a high cost of operation. Furthermore, the turbulent flow creates a hazard for the drivers of other vehicles when it is raining or snowing, or the roadway is wet, for in such a situation, the rain or snow and and any water splashed up from the roadway by the tires swirls around the tires and is thrown outwardly by the tires themselves and by the turbulent air flow. When this splashing and spraying water strikes the windshields of other vehicles, it lowers visibility for such motorists, and can cause them to lose control of their vehicles. Further, the spray raised by the rear tires reduces the truck driver's vision of the rear of the truck, making it more difficult for the truck driver to handle his vehicle when it's moving in traffic.
In recognition of the serious problem presented by the creation of spray by trucks, and particularly by multi-wheeled trailers, the Surface Transportation Act of 1982 has required that splash and spray be significantly reduced on trucks and trailers on highways.
The mechanical structure at the rear of a truck or trailer also creates stability problems, for the turbulent flow created by such structures interferes with the tracking of the rear wheels on wet or icy roadways. The rear wheels of a trailer are particularly susceptible to loss of control in yaw wind angles, where an angled cross wind strikes against the side of the trailer, and tends to blow it off track. The mechanical structure of the rear wheels, suspension and the like, cause such angled winds to interfere with the stability of the trailer, increasing the danger of serious handling problems.